In a news conference at the Shedd Aquarium, the mayor said that accomplishing this goal will require an enormous amount of hard work and cooperation and the commitment not only of government but also of every individual, business and institution in the city.

"We have a shared responsibility to protect our planet," Daley said. "We can't solve the world's climate change problem in Chicago, but we can do our part."

Officials say the Chicago metropolitan area, including the six surrounding counties, emits 103 million metric tons of greenhouse gases a year. The city of Chicago along emits 34.6 metric tons per year.

The Task Force that wrote the plan said Chicago needs to achieve an 80 percent reduction below its 1990 greenhouse gas emissions level by the year 2050 in order to do its part to avoid the worst global impacts of climate change.

To achieve this 80 percent reduction, the Task Force proposed an initial goal of a 25 percent cut in emissions below 1990 levels by 2020, a target that the mayor says is far enough in the future to allow time for major infrastructure and behaviorial changes, but soon enough to ensure the city is on the right course.

"Some of things we need to do, such as investing in transportation infrastructure, require the involvement of the state and federal government," Daley said. "But other important steps are much simpler and within the reach of each individual. These are things such as driving less and walking more, using energy-efficient light bulbs or turning down the thermostat a few degrees in the winter."

When he first took office in April 1989, the mayor said “climate change wasn't on the radar for most cities, states and nations around the world, or even for most people."

"But I believed then and believe even more deeply today that when you do such things as planting trees and creating open space, when you invest resources to remove pollution from the air and encourage the construction of buildings that are smart for the environment, then you enhance quality of life for all the residents of the city," Daley said.

Buildings emit 70 percent of all Chicago's greenhouse gas emissions and are the primary target of the Climate Action Plan.

Chicago City Hall is topped with a green roof, and the plan would increase rooftop gardens to a total of 6,000 buildings citywide and plant an estimated one million trees.

Between now and 2020, the plan calls for retrofit 50 percent of commercial and industrial building stock, resulting in a 30 percent energy reduction. All building renovations would be required to meet green standards, and water use efficiency in buildings would be upgraded as part of the retrofits.

The energy efficiency of 50 percent of residential buildings would be improved to achieve a 30 percent reduction in energy used, and appliance trade-in and lightbulb replacement programs would be expanded.

Chicago's Energy Conservation Code would be aligned with the latest international standards.

Daley said the city will move forward with right away with the Green Office Challenge that will spur high rise office buildings to save energy, increase recycling and water efficiency and reduce paper.

Other steps proposed in the plan and that the city is considering include large scale solar energy installations at city facilities and the construction of four publicly accessible alternative fueling stations.

The city is drafting a communications and outreach plan to engage all residents and businesses in the Chicago Climate Action Plan.

The city has launched a new website where Chicagoans and businesses can learn about climate change, what they can do in their daily lives to reduce emissions, and what the city is doing to protect the climate.